Modding tuning and best performance upgrades on the BMW M21D24 engine!

Tuners tips on "M21D24 Modifications"

M21D24 Modifications Guide

How to modify and upgrade the BMW M21D24

"Comprehensive guide to performance parts and tuning the BMW M21D24 engine!"

Sites like TorqueCars are regularly getting posts asking how to improve the M21D24 from people inquiring about getting more power from the M21D24 and wanting to know what are the things tuners are recommending when it comes to M21D24 mods that work. So let us look into BMW M21D24 parts and outline the best mods that work on this great engine and point out some problems along the way.

The BMW M21D24 really good project engines and with the best modifications like remapping, turbo upgrades and camshafts you will substantially enhance your driving fun.

In this article we review M21D24 tuning and outline the premier upgrades.

The greatest M21D24 parts on an engine are obviously the ones that give the biggest return for your money.

We won't be swayed by popular M21D24 parts, they need to be cost effective.

M21D24 induction kits

Improving air intake on the M21D24

You need air matched to fuel for an engine to work. If there is insufficient fuel then it will run lean, if there is too little air it runs rich resulting in lost power which risks damage to the M21D24. We'll pick up on fuelling later in this article but for now we shall look at air supply.

So it's important to any engine performance tuning task to pull air and fuel into your M21D24 but this has a knock on effect with the air flow sensor.

You'll commonly see there's a limitation in the air flow sensor AFM/MAF on the M21D24 when a lot more air is being fed into the engine.

We see 4 bar air sensors coping with quite large power gains, whereas the OEM air sensor limited performance at a much lower level.

Headers flow the on the suck phase from the filter and allow it to be drawn into the engine and mixed with fuel.

Design and rate of flow of the air Intake manifold can make a large effect on to fuel engine efficiency on the M21D24.

Most intake headers are crying out for performance upgrades, although some car makers provide well optimised intake headers.

Increasing the M21D24 valve size, doing a bit of M21D24 port enlargement and head flowing will also improve bhp, & more importantly will make space for increasing the bhp increase on other tuning parts.

M21D24 performance cam tips.

Each engine responds better to different cam durations so set your engine up on a rolling road.

The ECU mapping and fuel pump and injectors also will say much on the torque gains you'll get.

Altering valve durations can alter the torque band and on most engines the exhaust and intake durations do not need to match, although most cams and tuners use matched pairs there are some advantages to extending the intake or exhaust durations.

Significant air intake, and exhaust improvements on the M21D24 can be made from camshaft upgrades. Changing the camshaft profile alters the intake and exhaust durations on the engine and can dramatically change the power band and power output.

NB: Fast road camshafts normally bump the power over the rpm range, you may lose a little low down bhp but your high end rpm power will be better.

Race camshafts, bump the high end rpm power band but as a result the car will not idle smoothly and low end power nearly always suffers.

On a typical daily driver you should ideally to match your bhp range to your driving style.

I'd be surprised if you have ever thought a M21D24 Race cam is a pleasure to live with when in heavy traffic.

Stage 1, 2 and 3 mods for the M21D24

Before we break the best tuning upgrades down into stages of tune, let's list the most effective tuning upgrades for you.

  1. Suspension Upgrades - always improve your cars handling
  2. Brake Upgrades - Even before adding power improve those brakes
  3. Intake - make sure the intake is not restricted, use filters and intake upgrades to improve this
  4. Exhaust - as with 3 ensure there is not restriction in the exhaust, cats are the usual bottleneck
  5. Tunes - remapping, piggyback ECU's and aftermarket ECU's can all make decent gains
  6. Fuelling - when you've increased power you'll need to match this with more fuel
  7. Turbo upgrades - Improving the intake with a large turbo and better flowing intercooler will be the biggest power gain you'll see (but one of the most complex).

This video guide to tuning cars is a great starting point to work from in your project.

Stage 1 M21D24 parts:

Drilled & smoothed airbox, Sports exhaust manifold, Fast road camshaft, Remaps/piggy back ECU, Panel air filters, Intake headers.

Stage 2 M21D24 parts:

Ported and polished head, Sports catalyst & performance exhaust, fuel pump upgrades, induction kit, high flow fuel injectors, Fast road cam.

Tuning tips and articles Engine tuning Transmission tuning Care care Intake & exhaust mods Improve handling Forums

Stage 3 M21D24 parts:

Engine balancing & blueprinting, Crank and Piston upgrades to alter compression, Twin charging conversions, Internal engine upgrades (head flowing porting/bigger valves), Adding or Upgrading forced induction (turbo/supercharger), Competition cam.

Plan your options and then acquire your upgrades and set yourself a power target to avoid disappointment.

A remap helps fully realize the full potential of all the parts you've done to your M21D24.

You will typically expect to see gains of approximately 20-30% more power on turbocharged vehicles and you can expect to see around 15% on NASP engines, but your results may differs on the parts you've applied and the condition of your engine.

Turbo modifications on the M21D24

To get a turbo working on a NASP engine there is a lot involved, from lowering compression ratio to improved fuel supply and mapping, so we have found a great guide to helpavoid the common pitfalls or end up with an unfinished project because you were not told what you were getting into by doing this on the M21D24.

The more air you can get into an engine, the more fuel it can burn and uprating the induction with a turbocharger upgrade makes superb power gains.

When your motor is fitted with a turbo tuning parts are more reliable and most turbo engines use many forged and stronger components.

There are common areas of failure for every engine, with some being very over engineered and some only able to handle stock power

Discover these limits and fit forged components to utilize the power.

It's not unheard of car owners spending a loads of money on turbo charger upgrades on the M21D24 only to see the engine literally blow up on it's first outing after it's completed.

Large upgraded turbo units tend to suffer no power at low rpm, and little turbo units spool up really quickly but do not have the peak rpm power band gains.

Over the last 20 years the selection of turbos is always increasing and we commonly find variable vane turbos, allowing the vane angle is altered according to speed to lower lag and increase top end torque.

Twin scroll turbos divert the exhaust gases into a couple of channels and flow these at differently designed vanes in the turbo. They also boost the scavenging effect of the engine.

Beefing up the air intake by adding a supercharger or additional turbo will help you achieve very large bhp and torque gains, although more difficult to get working. We have this feature on twinchargers if you want to read more.

Tips about fuel supply on the M21D24

You will need to ensure that the engine is not starved of fuel so will have to pay attention to the fuelling when you start exceeding 20% of a torque hike. At this point we flag up the need to over specify your flow rate on the injectors.

As a rule of thumb add 15% capacity when specifying an injector, this takes into account injector deterioration and affords some spare capacity should the engine need more fuel.

Don't forget that different fuel grades will usually require different settings, a high octane fuel will burn more efficiently than lower octane fuel for example. A car will trim fuel supply to keep within the ideal air fuel mix but at the extreme ends you may need to adjust your injector capacity, or the mapping or you'll get flat spots and potential lean or rich fuel issues..

Recommended M21D24 performance exhaust upgrades

Only look to boost your exhaust system with an upgraded one is if the existing exhaust is actually causing a restriction in flow.

On most factory exhausts you'll find your flow rate is ok even on modest power gains, but on a serious tuning project with a big boost in power you will certainly need to get a better flowing exhaust.

Please dont run with the largest exhaust you can get you'll reduce the exhaust flow rate - the best exhausts for power gains are usually between one and a half to two and half inches. Your exhaust design, the bend angles and construction are what have more effect on flow rates than your pipe width to a certain extent. So the exhaust design is a big factor.

Usual exhaust restrictions come around the filters installed, so adding a faster flowing high performance alternative will help avoid this restriction.

Decatting (NB:catalysts reduce harmful engine emissions) is illegal in most countries and regions.

Faults issues and things to look out for on the M21D24

Like most engines an M21D24, should have few issues if it gets properly serviced and looked after.

We cannot stress enough the need for oil changes with the correct grade of oil on the M21D24, failure to do this will exacerbate engine wear, on a tuned M21D24 this is more important than ever and close attention should be paid to your maintenance schedule.

If you are interested in learning more or getting impartial tuning advice for your M21D24 why not pop over to the forums at TorqueCars where you can chat about M21D24 tuning options and read about others projects who may be planning to do similar modifications on their M21D24.

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